1. Field of the Invention
This invention relates generally to medium transferring systems and, more particularly, to a medium transferring system suitable for transferring with accuracy sheets of paper, such as bank notes, bank books or slips used in bank terminal equipment, or recording paper used in a printer, using a transferring means such as rubber rollers.
2. Related Art
In an ordinary process of transferring sheets of paper, the paper feed amount and other factors are adjusted each time when the feeding operation is performed, because the feeding accuracy depends upon the number of transferring operations, the kind of paper sheet to be dealt with, and so forth. Also, in a known system such as the one disclosed in Japanese Utility Model Unexamined Publication No. 62-41553, one of a plurality of modes predetermined on the basis of the thickness and the number of sheets to be transferred is selected with respect to one of the various types of media actually used, and the torque of a paper feeding motor is changed in accordance with the selected mode.
In this conventional art, the mode most suitable for each type of paper sheet is selected from a plurality of modes predetermined on the basis of the thickness and number of sheets, and the transferring torque is controlled on the basis of the selected mode. This system, however, fails to consider that the coefficients of friction between the paper sheet and transferring rollers are different in dependence on the types of paper sheet, which is one of the predominant factors in regard to changes in transference accuracy. This method is therefore defective in terms of the need to maintain a high degree of transference accuracy. In particular, there is a problem of spoiling due to character-printing deviations or of stain due to slippage in the process of transferring a bankbook in bank terminal equipment or transferring recording paper in a printer. There is another known system, such as the one disclosed in Japanese Patent Unexamined Publication No. 60-171950, in which a circuit designed to generate a rapid start signal so as to increase the rate at which the speed of a drive motor rises when the motor starts is provided in order to reduce the time lag associated with the rise in speed of a recording medium at the time of starting of feeding of the recording medium.
In the above-described conventional art, there are several items to be adjusted with respect to the transference of sheets of paper, e.g., one of relating to changes in the friction coefficient with different types of paper or with different number of transferring operations, or one relating to variations in the feed amount due to changes in humidity. Thus, a great deal of trouble is involved in regard to adjustment. Also, in the case of performing an operation to reduce the noises and the vibrations resulting from the rapid starting of the transferring of the medium and to shorten the time lag on starting, the variation of the amount of slippage influenced by the factors such as the change of the environmental values such as humidity and the reduction of the coefficient of friction of transferring means such as rubber rollers and the like due to increase of the numbers of operation becomes large, so that it is difficult to adjust the amount of the slippage. In the prior art, adequate consideration has not been taken to the above-described case and it is difficult to maintain a high degree of accuracy of the transferring.